Optical or lightwave communications systems are presently being intensively explored because of their promise for delivering greater quantities of information over a transmission medium than is possible with conventional electrical communications systems. Fundamental to any lightwave system is a lightwave source, such as a laser or an LED; a transmission medium, such as an optical fiber; and a detector, such as a semiconductor photodetector. Optical couplers are commonly used between the source and the detector for operating on the transmitted information (e.g., monitoring, amplifying). Devices such as lasers, LEDs and photodetectors that operate both electronically and optically are known as optoelectronic devices.
The U.S. patent of Blonder et al., U.S. Pat. No. 4,897,711, granted Jan. 30, 1990, describes a number of packaging subassemblies for optoelectronic devices that appropriately align an optoelectronic device with various lenses, reflectors, and optical fiber transmission media. The supports for various optoelectronic devices and the reflecting surfaces are defined in monocrystalline silicon by taking advantage of known anisotropic etching properties of silicon. Because silicon etches preferentially along predictable crystallographic planes, various grooves, cavities and alignment detents can be quickly and easily made with great precision by masking and etching various surfaces of monocrystalline silicon support structures.
Semiconductor lasers differ from semiconductor LEDs in that they emit light from a junction periphery in a direction parallel to the junction; whereas, LEDs emit light in a direction transverse to the junction through the "top" of the device. LEDs are commonly used in conjunction with multi-mode optical fibers for providing data communications (e.g., communication between computers); whereas, lasers are commonly used in conjunction with single-mode optical fibers to provide voice and voice-related communications.
Because LEDs emit light in the vertical direction, LED packages are somewhat difficult to make because, for structural reasons, it is preferred that the optical fiber extend from the package in a horizontal direction. Bending the fiber 90.degree. is poor practice for both structural and optical reasons. Thus, it is preferred that the LED package contain a reflector for changing the direction of the emitted light prior to transmission by the optical fiber.
The aforementioned Blonder et al. application shows in FIGS. 8 through 10 a number of optoelectronic device packages for supporting an LED such that its output is reflected into an optical fiber. While the structures shown can be easily made, they do not provide for the most efficient coupling of light into an optical fiber because the light from the LED is directed into the optical fiber at an angle with respect to the fiber axis. The most efficient coupling requires that the light be directed into the optical fiber in a direction that is parallel to the axis of the optical fiber. Accordingly, there is a need for an optical device package that is easy to make with great precision and yet provides for efficient optical coupling between an LED or other optoelectronic device and an optical fiber.